There is an increasing demand for systems for military, private or individual use that are capable of detecting and analyzing chemical and biological contaminants, such as explosives (e.g., TNT or DNT). One method of detecting such contaminants uses rotational microwave spectroscopy. The rotational and vibrational modes of molecules (e.g., contaminant molecules) have energies that naturally correspond to energies of photons in a spectrum of radiation. A source generates radiation that interacts with contaminant molecules present in a “target” to be analyzed, so that specific frequencies of emitted radiation are absorbed by the molecules. A detector is positioned to identify the frequencies that fail to transmit through the target, and the failure of a particular frequency to transmit can indicate the presence of a specific absorbing contaminant.
The far infrared (or terahertz) spectrum of radiation is particularly well-suited for use in systems such as that described above, because the spectrum corresponds to the vibrational and rotational modes of many chemicals, including explosives, and contains a great deal of signature information. Unfortunately, work in the terahertz spectrum is made extremely difficult and inconvenient by a lack of coherent sources of radiation that can operate continuously and tune over a wide range of the terahertz wavelength spectrum.
Therefore, there is a need in the art for a terahertz system that can be used to detect the presence of chemical and biological contaminants.